JP6639544B2 - L2MX-type complexes as phosphorescent dopants for organic LEDs - Google Patents

Abstract

A phosphorescent compound having the formula L 2 MX, wherein: M is a metal that forms octahedral complexes; L is a monoanionic bidentate ligand, which is bonded to M through an sp 2 hybridized carbon and a heteroatom; X is a monoanionic bidentate ligand; and L and X are inequivalent.

Description

I. (Technical field)
The present invention relates to organometallic compounds of the formula L ₂ MX, where L and X are different bidentate ligands and M is a metal, especially iridium, their synthesis, and dopants in certain hosts. As a method for forming a light emitting layer of an organic light emitting device.

II. (Background technology)
II. A. General Background Organic light emitting devices (OLEDs) are composed of several organic layers, one of which can be made to emit electroluminescence by applying a voltage through the device. It is composed of materials. C. W. Tang et al., Appl. Phys. Lett., 51, 913, (1987). Certain OLEDs have been shown to have sufficient brightness, color range, and operating life to be used as a viable alternative to LCD-based full-color panel displays [S. R. Forrest, P.M. E. FIG. Burrows; E. FIG. Thompson, Laser Focus World, Feb. (1995)]. Since many of the organic thin films used in such devices are transparent in the visible spectral range, they are in the form of vertically stacked OLEDs emitting red (R), green (G), and blue (B). An entirely new type of display pixel can be realized that provides a simple manufacturing method, a small RGB pixel size, and a large filling factor. International Patent Application No. PCT / US95 / 15790.

  Transparent OLEDs (TOLEDs), which represent an important step in achieving independently addressed addressable stacked RGB pixels, are disclosed in International Patent Application No. PCT / US97 / 02681, where the TOLED shows greater than 71% transparency when switched off, and with high efficiency (quantum efficiency close to 1%) when the device is switched on. And emit light from both the device surface below. The TOLED uses a transparent indium tin oxide (ITO) as a hole injection electrode and an Ng-Ag-ITO electrode layer for electron injection. A device is disclosed wherein the ITO side of the Ng-Ag-ITO layer is used as a hole injection contact for a second alternative color emitting OLED stacked on the TOLED. Each layer of a stacked OLED (SOLED) is independently addressable and emits its own characteristic color. This colored emission is transmitted through the adjacent stacked transparent and independently addressable organic layer (s), transparent contacts, and glass substrate, and the relative output of the red and blue light emitting layers To allow the device to emit any color that can be produced by changing the color.

  The PCT / US95 / 15790 application discloses an integrated SOLED in which both intensity and color can be independently changed and adjusted with externally supplied power in a color-adjustable display device. Thus, the PCT / US95 / 15790 application illustrates the principle of achieving an integrated full color pixel that provides the large resolution enabled by the small pixel size. Further, relatively low cost manufacturing techniques can be used to manufacture such devices as compared to conventional methods.

International Patent Application No. PCT / US95 / 15790 International Patent Application No. PCT / US97 / 02681

C. W. Tang et al., Appl. Phys. Lett., 51, 913 (1987). S. R. Forrest, P. E. Burrows, and M. E. Thompson, Laser Focus World, Feb. (1995)

II. B. Luminous background
II. B. 1. Foundation
II. B. 1. a. Singlet and triplet excitons Since light is generated in organic materials due to molecular excited states or the decay of excitons, understanding their properties and interactions is critical to their potential in displays, lasers, and other lighting applications. It is important for the design of efficient light-emitting devices, which are currently of great interest for commercial applications. For example, if the symmetry of the exciton is different from that of the ground state, radiative relaxation of the exciton becomes impossible, and luminescence becomes slow and inefficient. Since the ground state is usually antisymmetric in the exchange of electron spins containing excitons, decay of symmetric excitons breaks symmetry. Such excitons are known as triplets, and this term reflects the degeneracy of that state. For any three triplet excitons formed by electrical excitation in the OLED, only one symmetric state (ie, singlet) exciton occurs. [M. A. Baldo, D.C. F. O'Brien, M .; E. FIG. Thompson, and S.M. R. Forrest, `` Very high-efficiency green organic light-emitting devices based on electrophosphorescence, '' Applied Physics Letters, 75, 4-6, (1999) . Luminescence from the unsymmetrical process is known as phosphorescence. Characteristically, phosphorescence has a low probability of transition and may last up to several seconds after excitation. Fluorescence, on the other hand, comes from the fast decay of singlet excitation. It is very efficient because this process takes place between the same states of symmetry.

  Many organic materials show fluorescence from singlet excitons. However, it has also been found that only a few can provide effective room temperature phosphorescence due to triplets. For example, for most fluorescent dyes, the energy contained in the triplet state is wasted. However, when the triplet excited state causes a perturbation, for example, due to spin-orbit coupling (typically caused by the presence of heavy metal atoms), effective phosphorescence is more likely to occur. In this case, the triplet excitation takes on some singlet properties, which have a greater probability of radioactive decay to the ground state. In fact, phosphorescent dyes having these properties exhibit high efficiency of electroluminescence.

  Only a few organic materials have been shown to exhibit effective room temperature phosphorescence due to triplets. In contrast, many fluorescent dyes are known [C. H. Chen, J.M. Shi, and C.I. W. Tang, "Recent developments in molecular organic electroluminescent materials", Macromolecular Symposia., 125, 1-48, (1997); Blackman, "Lambdachrome Laser Dyes", Lambda Physik, Göttingen, 1997]. It is not unusual for fluorescence efficiency in solution to approach 100% ( CH Chen, 1997, supra). Fluorescence is unaffected by triplet-triplet annihilation, which reduces phosphorescence at large excitation densities [M. A. Bard et al., "High efficiency phosphorescent emission from organic electroluminescent devices", Nature, 395, 151-154, (1998); A. Bardo, M. E. FIG. Thompson, and S.M. R. Forrest, "An analytic model of triplet-triplet annihilation in electrophosphorescent devices", 1999]. Thus, the fluorescent materials are suitable for many electroluminescent applications, especially for passive matrix displays.

II. B. 1. b. Overview of the Basis of the Present Invention The present invention relates to compounds of the formula LL′L ″ M where L, L ′ and L ″ are different bidentate ligands and M is more than 40 to form an octahedral complex. High atomic number metals, preferably the metals of the third transition metal of the transition series of the periodic table]. Alternatively, M can be a metal of a second series transition metal, or main group metals, such as Zr and Sb. Some such organometallic complexes exhibit electroluminescence and exhibit luminescence coming from the lowest energy ligand or MLCT state. Such an electroluminescent compound can be used as a dopant in a host layer of a light emitting layer of a light emitting diode. The invention further relates to a compound of the formula LL′L ″ M, wherein L, L ′ and L ″ are the same or different, wherein L, L ′ and L ″ are monoanionic bidentate ligands. , M is a metal forming an octahedral complex, preferably a metal of the third series of transition metals, more preferably Ir or Pt, and the atoms coordinating the ligands are sp ² hybridized orbitals. ) Consisting of carbon and heteroatoms). The invention further relates to L ₂ MX wherein L and X are different bidentate ligands, and L is coordinated to M by an atom of L having a sp ² hybrid orbital carbon and a heteroatom; Is a metal which forms an octahedral complex, preferably iridium (Ir). These compounds can act as dopants in a host layer that acts as a light emitting layer of an organic light emitting diode.

The compounds of the present invention has the formula _{L 2 M (μ-Cl)} 2 ML 2 ( wherein, L is a bidentate ligand, M is a metal such as Ir) and chloride crosslinked dimers, It can be produced by a direct reaction with a substance XH that functions to introduce a bidentate ligand X. XH can be, for example, acetylacetone, 2-picolinic acid, or N-methylsalicylanilide, where H represents hydrogen. The resulting product has the formula L ₂ MX, where an octahedral coordination of the bidentate ligands L, L and X around M can be obtained.

The resulting compound of formula L ₂ MX can be used as phosphorescent emitters in organic light emitting devices. For example, compounds where L = (2-phenylbenzothiazole), X = acetylacetonate, and M = Ir (compounds abbreviated as BTIr) are 4,4 ′ to form a light emitting layer in an OLED. When used as a dopant in -N, N'-dicarbazole-biphenyl (CBP) (at a level of 12% by mass), it exhibits a quantum efficiency of 12%. For reference, the formula CBP is as follows:

The synthesis method for producing L ₂ MX can be advantageously used when L itself is a phosphor but the resulting L ₂ MX is a phosphor. One particular example of this is when L = coumarin-6.

  This synthesis facilitates the coupling of L and X pairs with certain desired properties.

By appropriate selection of L and X, the color of complex L ₂ MX relative to L ₃ M can be adjusted. For example, both Ir (ppy) ₃ and (ppy) ₂ Ir (acac) give a strong green emission with a λ _max of 510 nm [ppy represents phenylpyridine]. However, when the X ligand is formed from picolinic acid, rather than from acetylacetone, there is a small blue shift of about 15 nm.

Furthermore, X is without degrading the emission quality, as carriers (holes or electrons) are trapped in X (or L), to L 3 _M complex, selected to have a certain HOMO level be able to. In this way, carriers (holes or electrons) that would otherwise cause harmful oxidation or reduction of the phosphor will be blocked. Carriers trapped at a distance will readily recombine with intermolecularly oppositely-signed carriers, or with carriers from neighboring molecules.

  The invention and its various aspects are discussed in more detail in the examples below. However, the embodiments can be operated by different mechanisms. The various mechanisms by which the various aspects of the present invention operate are discussed without, however, limiting the scope of the present invention.

II. B. 1. c. Dexter and Foerster Mechanisms Discussing the theory of the underlying energy transfer mechanism will help to understand the different aspects of the present invention. Two mechanisms are generally discussed for transferring energy to the receptor molecule. Dexter movement [D. L. In the first mechanism of Dexter, A theory of sensitized luminescence in solids, J. Chem. Phys., 21, 836-850, (1953) You can jump directly from one molecule to the next. This is a short-range process that depends on the overlap of the molecular orbitals of adjacent molecules. It also retains the symmetry of the donor-acceptor pair [E. Wigner and E.W. W. Wittmer, "Structure of diatomic molecular spectra by quantum mechanics" (Uber die Struktur der zweiatomigen Molekelspektren nach der Quantenmechanik), Zeitshrift fur Physik, 51, 859-886, (1928); Klessinger and J.M. Michl, "Excited states and photochemistry of organic molecules" (VCH Publishing Company, New York, 1995). Therefore, the energy transfer of the formula (1) is impossible by the Dexter mechanism. In the second mechanism of Forster movement, [T. Forster, "Intermolecular energy transfer and fluorescence" (Zwischenmolekulare Energiewanderung and Fluoreszenz), Annalen der Physik, 2, 55-75 (1948); Forster, "Fluorescence of Organic Compounds" (Fluoreszenz organischer Verbindugen) (Vandenhoek and Ruprecht, Göttingen, 1951)], and energy transfer of formula (1) is possible. In Forster movement, the dipoles of the donor and acceptor molecules combine, as well as the transmitter and antenna, and the energy can move. Dipoles arise from allowed transitions in both donor and acceptor molecules. This will typically limit the Forster mechanism to movement between singlet states.

  Nevertheless, as long as the phosphor can emit light due to some perturbation of the state, such as by spin-orbit coupling introduced by heavy metal atoms, it may also serve as a donor in Forster transfer. Can be. The efficiency of this process is determined by the luminescence efficiency of the phosphor [F. Wilkinson, "Advances in Photochemistry", W.W. A. Noise, No. Hammond, and J.M. N. Pitts Edit, John Wiley & Sons, New York, 1964, pp. 241-268], ie, if a radioactive transition is more likely to occur than a non-radioactive decay, the energy transfer will be effective. Such triplet-singlet transfer has been predicted by Forster [T. Forster, `` Transfer mechanisms of electronic exitation, '' Discussions of the Faraday Society, 27, 7-17, (1959)), Ermolaev (S.E.) and Sveshnikova (S.). V. L. Elmoraev and E.A. B. Sveshnikova, `` Inductive-resonance transfer of energy from aromatic molecules in the triplet state '', Doklady Akademii Nauk SSSR, 149, 1295-1298, (1963)), Detected energy transfer at 77K or 90K using a range of phosphorescent donors and fluorescent acceptors in a solid medium. Long distance migration has been observed, for example, using triphenylamine as donor and chrysoidin as acceptor, the interaction range is 52 °.

The remaining condition for Forster transfer is that the absorption spectrum overlaps the emission spectrum of the donor, assuming that the energy levels between the excited and ground state molecule pairs are in resonance. In Example 1 of the present application, we used the green phosphor fac tris (2-phenylpyridine) iridium [Ir (ppy) ₃ ; A. Baldo, et al., Appl. Phys. Lett., 75, 4-6, (1999)], and a red fluorescent dye, [2-methyl-6- [2- (2,3,6,7-tetrahydro) C.-1H, 5H-benzo [ij] quinolin-9-yl) ethenyl] -4H-pyran-ylidene] propane-dinitrile] ["DCM2"; W. Tang, S.M. A. Van Slyke, and C.I. H. Chen, "Electroluminescence of doped organic films", J. Appl. Phys., 65, 3610-3616, (1989)]. DCM2 absorbs in the green and due to the local polarization field it emits at a wavelength between λ = 570 nm and λ = 650 nm [V. Bulovic et al., `` Bright, saturated, red-to-yellow organic light-emitting devices based on polarization-induced spectral shifts '', Chem. Phys. Lett., 287, 455-460, (1998)].

  By doping a fluorescent guest into the phosphorescent host material, it becomes possible to transfer Forster energy from the triplet state. Unfortunately, such systems are affected by competing energy transfer mechanisms that reduce overall efficiency. In particular, the close proximity of the host and guest increases the likelihood of Dexter transfer from the host to the guest triplet. As the excitons approach the guest triplet state, they are effectively lost. This is because these fluorescent dyes typically exhibit extremely inefficient phosphorescence.

  In order to maximize the transfer of the host triplet to the fluorescent dye singlet, it is desirable to maximize the Dexter transfer of the phosphor to the triplet state while minimizing the transfer of the fluorescent dye to the triplet state. Since the Dexter mechanism transfers energy between adjacent molecules, reducing the concentration of the fluorescent dye reduces the probability of triplet-triplet transfer to the dye. On the other hand, long-range Forster movement to the singlet state is not affected. In contrast, the transfer of the phosphor to the triplet state is necessary to utilize the host triplet and can be improved by increasing the concentration of the phosphor.

II. B. 2. Correlation Between Device Structure and Emission Devices with structures based on the use of layers of organic optoelectronic materials generally rely on general mechanisms to provide optical emission. This mechanism is typically based on luminescent recombination of the trapped charge. In particular, OLEDs have at least two thin organic layers separating the anode and cathode of the device. One material of these layers is a “hole transport layer” (HTL), which is selected based on, inter alia, the material's ability to transport holes, while the material of the other layer is specifically selected according to its ability to transport electrons. "Electron transport layer" (ETL). With such a structure, the device can be viewed as a diode and becomes forward biased when the potential applied to the anode is higher than the potential applied to the cathode. Under these bias conditions, the anode injects holes (positive charge carriers) into the hole transport layer, while the cathode injects electrons into the electron transport layer. Thus, the portion of the luminescent medium adjacent to the anode forms a hole injection and transport region, while the portion of the luminescent medium adjacent to the cathode forms an electron injection and transport region. The injected holes and electrons move toward the oppositely charged electrodes, respectively. When electrons and holes are localized on the same molecule, Frenkel excitons are formed. This short-lived recombination is visible when electrons fall from their conduction potential into the valence band, and under certain conditions relaxation occurs preferentially by the luminescence mechanism. According to this view of the working mechanism of a typical thin-layer organic device, the electroluminescent layer has a luminescent region that receives mobile charge carriers (electrons and holes) from each electrode.

  As mentioned above, the emission from the OLED is typically due to fluorescence or phosphorescence. There is a problem with the use of phosphorescence. It has been observed that at high current densities, the phosphorescence efficiency drops rapidly. A long phosphorescence lifetime causes saturation of the light emitting site, and triplet / triplet annihilation also causes a decrease in efficiency. Another difference between fluorescence and phosphorescence is that the triplet energy transfer from the conductive host to the luminescent guest molecule is typically slower than that of the singlet. Long-range dipole-dipole coupling (Forster transfer) that governs singlet energy transfer is forbidden for triplets due to (theoretically) the principle of spin symmetry conservation. Thus, in the triplet case, energy transfer typically occurs by exciton diffusion into adjacent molecules (Dexter transfer), and considerable overlap of the donor and acceptor excitation wavefunctions results in energy transfer. Is required. Another problem is that the triplet diffusion distance is typically longer (eg,> 1400 °) compared to a typical singlet diffusion distance of about 200 °. Therefore, in order for a phosphorescent device to be able to realize those possibilities, the device structure needs to be optimal for triplet characteristics. In the present invention, the property of long-range triplet diffusion is used to improve external quantum efficiency.

  Successful use of phosphorescence promises enormous prospects for organic electroluminescent devices. For example, the advantage of phosphorescence is that all of the triplet-based excitons (formed by the recombination of holes and electrons in the EL) of the phosphorescent device are partially converted to energy by certain electroluminescent materials. Being able to participate in movement and luminescence. In contrast, singlet-based fluorescent devices result in only a small percentage of excitons giving fluorescence luminescence.

  Another method is to utilize a phosphorescence process to increase the efficiency of the fluorescence process. Fluorescence is in principle 75% less efficient with a number three times larger than the symmetrically excited state.

II. C. Material background
II. C. 1. Basic Heterostructure Since there is typically at least one electron transport layer and at least one hole transport layer, there are layers of different materials forming the heterostructure. The material that generates the electroluminescence emission is the same material as the material that functions as the electron transport layer or the hole transport layer. Such a device in which the electron transporting or hole transporting layer also acts as a light emitting layer is referred to as having a single heterostructure. Alternatively, the electroluminescent material may be in a separate emissive layer between the hole transport layer and the electron transport layer, which is called a double heterostructure. The other emissive layer may include emissive molecules doped into the host, or the emissive layer may consist essentially of emissive molecules only.

  That is, in addition to the light-emitting material, which is present as a main component in the charge carrier layer, i.e., the hole-transporting layer or the electron-transporting layer, and functions as both a charge carrier material and a light-emitting material, a relatively large amount of dopant in the charge carrier layer is used. The light emitting material may be present at a low concentration. When a dopant is present, the primary material in the charge carrier layer can be referred to as a host or accepting compound. The materials present as host and dopant are selected to provide a high level of energy transition from the host to the dopant material. Furthermore, these materials need to be able to produce acceptable electrical properties for OLEDs. Furthermore, such host and dopant materials can preferably be introduced into the OLED using convenient manufacturing techniques, especially using materials that can be easily incorporated into the OLED using vacuum deposition techniques. .

II. C. 2. Exciton blocking layer An exciton blocking layer is provided in the OLED device to substantially hinder the diffusion of the exciton, thereby substantially retaining the exciton in the emissive layer and increasing the efficiency of the device. You can enter. The material of the blocking layer is characterized by an energy difference (bandwidth) between its lowest unoccupied orbit (LUMO) and its highest occupied orbit (HOMO). While this bandgap substantially prevents exciton diffusion through the blocking layer, it has minimal effect at the switched-on voltage of the completed electroluminescent device. Therefore, the band gap is preferably greater than the energy level of the excitons generated in the light emitting layer, so that such excitons cannot be present in the blocking layer. In particular, the band gap of the blocking layer is at least as large as the energy difference between the triplet state and the ground state of the host.

  In the state where the blocking layer exists between the hole conductive host and the electron transport layer, the following properties listed in order of relative importance are required.

1. The energy difference between the LUMO and HOMO of the blocking layer is larger than the energy difference between the triplet and the ground state singlet of the host material.
2. Triplets in the host material are not quenched by the blocking layer.
3. The ionization potential (IP) of the blocking layer is greater than the ionization potential of the host (meaning that holes are retained in the host).
4. The LUMO energy level of the blocking layer and the LUMO energy level of the host are sufficiently close in energy so that the change in total conductivity of the device is less than 50%.
5. The blocking layer is made as thin as possible, provided that it has a layer thickness sufficient to effectively block exciton transfer from the emissive layer to the adjacent layer.

  That is, to block excitons and holes, the ionization potential of the blocking layer should be greater than that of the HTL, and at the same time the electron affinity of the blocking layer will be approximately equal to that of the ETL to facilitate transport of electrons. Should be. [If a radioactive (luminescent) molecule is used without a hole transport host, the above rules for selecting a blocking layer are modified by replacing the word “host” with “luminescent molecule”. ]

  For auxiliary states using a blocking layer between the electron conducting host and the hole transport layer, determine their properties (listed in order of importance):

1. The energy difference between the LUMO and HOMO of the blocking layer is larger than the energy difference between the triplet and the ground state singlet of the host material.
2. Triplets in the host material are not quenched by the blocking layer.
3. The LUMO energy of the blocking layer is greater than the LUMO energy of the (electron transport) host. (Meaning that the electrons are held in the host).
4. The ionization potential of the blocking layer and the ionization potential of the host are such that holes are easily injected from the barrier into the host and the change in the overall conductivity of the device is less than 50%.
5. The blocking layer is made as thin as possible, provided that it has a layer thickness sufficient to effectively block exciton transfer from the emissive layer to the adjacent layer.

  [If a radioactive (luminescent) molecule is used without an electron transporting host, the above rules for selecting a blocking layer are modified by replacing the word “host” with “luminescent molecule”. ]

II. D. With respect to color, OLEDs are manufactured using materials that provide a relatively narrow band of electroluminescent emission centered near a selected spectral region corresponding to one of the three main colors, red, green and blue. However, it is desirable that they can be used as colored layers in OLEDs or SOLEDs. It would also be desirable to be able to easily deposit such compounds as thin layers using vacuum deposition techniques and to easily incorporate them into OLEDs made entirely from vacuum deposited organic materials.

  U.S. Patent Application Serial No. Ser. 08 / 774,333 (approved) relates to OLEDs containing a luminescent compound that produces a saturated red emission.

III. (Disclosure of the Invention)
At a general level, the invention relates to complexes of metal M having an atomic number greater than 40, where M forms an octahedral complex having three bidentate ligands. Metals include main group metals such as Sb, "second series transition metals of the periodic table transition series", preferably "third series transition metals of the periodic table transition series", and most preferably Ir and Pt. included. The organometallic complex can be used in a light emitting layer of an organic light emitting diode. The complex can be depicted as LL′L ″ M, where L, L ′ and L ″ represent a bidentate ligand and M represents a metal. An example in which all ligands are different is shown in FIG.

The invention further relates to an organometallic complex of a metal species M with a monoanionic bidentate ligand, wherein M is coordinated with the sp ² hybrid orbital carbon and heteroatom of the ligand. Complexes include L ₃ M (where each ligand L substance is the same), LL′L ″ M (where each ligand substance L, L ′, L ″ is different), Alternatively, it may be in the form of L ₂ MX, where X is a monoanionic bidentate ligand. Ligand L is generally expected to be more involved in the emission process than X. Preferably, M is a third series of transition metals, and most preferably, M is Ir or Pt. The invention also relates to the meridianal isomer of L ₃ M, wherein the heteroatoms (eg nitrogen) of the two ligands L are in trans form. In the embodiment in which the sp ² hybrid orbital carbon and the hetero atom of the ligand are coordinated to M, the ring having the metal M, the sp ² hybrid orbital carbon and the hetero atom preferably has 5 or 6 atoms.

Furthermore, the present invention relates to the use of a complex of a transition metal substance M having bidentate ligands L and M as a compound of the formula L ₂ MX in the light-emitting layer of an organic light-emitting diode. Preferred embodiments are compounds of formula L ₂ IrX as configured dopant in a host layer to serve as a light emitting layer in an organic light emitting diode (wherein, L and X are bidentate ligands different) It is.

The present invention also relates to an improved synthesis of organometallic molecules that serve as a light emitter in a light emitting device. The compound of the present invention reacts with the following reaction: L ₂ M (μ-Cl) ₂ ML ₂ + XH → L ₂ MX + HCl [wherein L ₂ M (μ-Cl) ₂ ML ₂ is a bidentate ligand of L And XH is a Bronsted acid that reacts with the crosslinked chloride to introduce the bidentate ligand X, wherein XH Can be, for example, acetylacetone, 2-picolinic acid, or N-methylsalicylanilide. ]. The method _includes binding the _{L 2 M (μ-Cl)} 2 ML 2 chloride crosslinked dimers, and XH material. L ₂ MX has a nearly octahedral arrangement of bidentate ligands L, L, and X around M.

The present invention further as phosphorescent emitters in organic light emitting devices, relates to the use of a compound of formula L ₂ MX. For example, a compound in which L = (2-phenylbenzothiazole), X = acetylacetonate, and M = Ir (abbreviated as BTIr) is used as a dopant in CBP to form a light emitting layer in an OLED. When used (at a level of 12% by mass), it exhibits a quantum efficiency of 12%. For reference, the formula for 4,4′-N, N′-dicarbazole-biphenyl (CBP) is as follows:

The present invention further relates to an organometallic complex L ₂ MX, in this case L itself is a phosphor, resulting L ₂ MX is phosphor. One particular example of this is when L = coumarin-6.

The present invention further relates to the appropriate selection of L and X for L ₃ M in order to control the color of the complex L ₂ MX. For example, both Ir (ppy) ₃ and (ppy) ₃ Ir (acac) give a strong green emission with a λ _max of 510 nm [ppy represents phenylpyridine]. However, when the X ligand is formed from picolinic acid, rather than from acetylacetone, there is a small blue shift of about 15 nm.

Furthermore, without causing deterioration of the light-emitting quality, as carriers (holes or electrons) are trapped in X (or L), to L 3 _M complex, selecting X to have a certain HOMO level About. In this way, carriers (holes or electrons) that would otherwise cause harmful oxidation (or reduction) of the phosphor will be blocked. Carriers trapped at a distance will readily recombine with intermolecularly oppositely-signed carriers, or with carriers from neighboring molecules.

  IV. BRIEF DESCRIPTION OF THE FIGURES

FIG. 3 shows the predicted structures of the L ₂ IrX complexes along with the predicted structures for PPir, and also shows four examples of X ligands used for these complexes. The structure shown is for an acac derivative, for other X-type ligands, replace the OO ligand with the NO ligand. FIG. 2 shows a comparison of facial and meridianal isomers of L ₃ M. FIG. ₃ is a diagram showing the molecular formulas of the mer isomers disclosed herein: mer-Ir (ppy) ₃ and mer-Ir (bq) ₃ . PPY (or ppy) represents phenylpyridyl, and BQ (or bq) represents 7,8-benzoquinoline. mer-Ir _(ppy) is a diagram showing a model of ₃ and _{(ppy) 2 Ir (acac)} . FIG. 5A is a diagram showing data (quantum efficiency vs. current density) of an electroluminescent device when “BTIr” of 12% by mass is put in CBP. BTIr stands for bis (2-phenylbenzothiazole) iridium acetylacetonate. FIG. 5B shows an emission spectrum from the device of FIG. 5A. FIG. 3 is a diagram of a representative molecule for trapping holes. It is a figure which shows the emission spectrum of Ir (3-MeOppy) ₃ . It is a figure which shows the emission spectrum of tpyIrsd. It is a figure which shows the proton NMR spectrum of tpyIrsd (= typIrsd). It is a figure which shows the emission spectrum of thpyIrsd. It is a figure which shows the proton NMR spectrum of thpyrIrsd. It is a figure which shows the emission spectrum of btIrsd. It is a figure which shows the proton NMR spectrum of btIrsd. It is a figure which shows the emission spectrum of BQIr. It is a figure which shows the proton NMR spectrum of BQIr. It is a figure which shows the emission spectrum of BQIrFA. It is a figure which shows the emission spectrum of THIr (= thpy; THPIr). It is a figure which shows the proton NMR spectrum of THPIr. It is a figure which shows the emission spectrum of PPir. It is a figure which shows the proton NMR spectrum of PPir. It is a figure which shows the emission spectrum of BTHPIr (= BTPIr). It is a figure which shows the emission spectrum of tpyIr. FIG. 3 is a diagram showing a crystal structure of tpyIr showing a trans-type arrangement of nitrogen. It is a figure which shows the emission spectrum of C6. It is a figure which shows the emission spectrum of C6Ir. It is a figure which shows the emission spectrum of PZIrP. It is a figure which shows the emission spectrum of BONIr. It is a figure which shows the proton NMR spectrum of BONIr. It is a figure which shows the emission spectrum of BTIr. It is a figure which shows the proton NMR spectrum of BTIr. It is a figure which shows the emission spectrum of BOIr. It is a figure which shows the proton NMR spectrum of BOIr. It is a figure which shows the emission spectrum of BTIrQ. It is a figure which shows the proton NMR spectrum of BTIrQ. It is a figure which shows the emission spectrum of BTIrP. It is a figure which shows the emission spectrum of BOIrP. It is a figure which shows the emission spectrum of a btIr type complex which has a different ligand. It is a figure which shows the proton NMR spectrum of mer-Irbq. FIG. 3 shows other suitable L and X ligands for L ₂ MX compounds. It is a figure which shows the example of a LL'L "M compound.

V. (Detailed description of the present invention)
V. A. Chemical present invention relates to the synthesis and use of the formula L ₂ MX certain organometallic molecules can be doped into the light emitting layer host layer of an organic light emitting diode. Optionally, the molecules of formula L ₂ MX is the increased concentrations, or as such, can be used for the light-emitting layer. The present invention relates to a compound of the formula L ₂ MX, wherein L and X are different bidentate ligands and M forms an octahedral complex, preferably selected from the third row of transition elements of the periodic table An organic light-emitting device having a light-emitting layer containing molecules of a metal, most preferably Ir or Pt), said light-emitting layer producing a light emission having a maximum at a certain wavelength λ _max .

V. A. 1. The general chemical formula for the molecule doped into the dopant host phase is L ₂ MX, where M is a transition metal forming an octahedral complex, L is a bidentate ligand, and X is a different bidentate Is a ligand).

  Examples of L include 2- (1-naphthyl) benzoxazole, (2-phenylbenzoxazole), (2-phenylbenzothiazole), (2-phenylbenzothiazole), (7,8-benzoquinoline), coumarin, (Thienylpyridine), phenylpyridine, benzothienylpyridine, 3-methoxy-2-phenylpyridine, thienylpyridine, and tolylpyridine.

  Examples of X are acetylacetonate (acac), hexafluoroacetylacetonate, salicylidene, picolinate, and 8-hydroxyquinolinate.

  Yet another example of L and X is given in FIG. 39, and yet another example of L and X is “Comprehensive Coordination Chemistry” (Editor G. Wilkinson, Pergamon Press), Vol. Especially M.I. Calligaris and L. Chapter 20.1 (from page 715) by Randaccio and S. It can be found in Section 20.4 by Vagg (pages 793 et seq.).

V. A. 2. Synthetic V. of the molecule of formula _L 2 MX A. 2. a. Compounds of Reaction Scheme formula L ₂ MX can be prepared according to the following formula:
L ₂ M (μ-Cl) ₂ ML ₂ + XH → L ₂ MX + HCl [where L ₂ M (μ-Cl) ₂ ML ₂ is a chloride-bridged dimer having L as a bidentate ligand , M is a metal such as Ir; XH is a Bronsted acid which reacts with the bridging chloride to serve to introduce the bidentate ligand X, wherein XH is, for example, acetylacetone, hexafluoroacetylacetone, It can be 2-picolinic acid or N-methylsalicylanilide. L ₂ MX has a nearly octahedral arrangement of bidentate ligands L, L, and X around M.

V. A. 2. b. Example L ₂ Ir (μ-Cl) ₂ IrL ₂ complex was prepared from IrCl ₃ .nH ₂ O and the appropriate ligand by literature methods [S. Sprouse, K.S. A. King, P.M. J. Spellane, R.A. J. Watts, J. Am. Chem. Soc., 106, 6647-6653, (1984); A. Carlson et al., Inorg. Chem., 32, 4483, (1993); Schmid et al., Inorg. Chem., 33, 9, (1993); Garces et al., Inorg. Chem., 27, 3464, (1988); G. FIG. Colombo et al., Inorg. Chem., 32, 3088, (1993); Mamo et al., Inorg. Chem., 36, 5947, (1997); Seroni, et al., J. Am. Chem. Soc., 116, 9086, (1994); P. Wilde et al., J. Phys. Chem., 95, 629, (1991); H. Van Diemen et al., Inorg. Chem., 31, 3518, (1992); G. FIG. Colombo et al., Inorg. Chem., 33, 545, (1994)].

Ir (3-MeOppy) ₃ . _{Ir (acac) 3 (0.57g,} 1.17mM) and 3-methoxy-2-phenylpyridine (1.3g, 7.02mM) were mixed in glycerol 30 ml, 24 h 200 ° C. in a _{N 2} Heated. The resulting mixture was added to 100 ml of 1M HCl. The precipitate was collected by filtration, using _CH 2 Cl ₂ was purified by column chromatography as eluent to give the product as a light yellow solid (0.35g, 40%). MS (EI): m / z ( relative ^{intensity) 745 (M -, 100)} , 561 (30), 372 (35). The emission spectrum is shown in FIG.

tpyIrsd. Chloride cross-linked dimer (tpyIrCl) ₂ (0.07 g, 0.06 mM), salicylidene (0.022 g, 0.16 mM) and Na ₂ CO ₃ (0.02 g, 0.09 mM) were added to 10 ml of 1, Mix in 2-dichloroethane and 2 ml ethanol. The mixture until no dimer was detected by TLC, was refluxed in 6 h N _2. Then the reaction was cooled and the solvent was evaporated. Excess salicylidene was removed by gentle heating in vacuo. The residual solid was redissolved in CH ₂ Cl ₂ and insoluble inorganics were removed by filtration. The filtrate was concentrated and subjected to column chromatography using _CH 2 Cl ₂ as eluent to give the product as a light yellow solid (0.07g, 85%). MS (EI): m / z (relative intensity) 663 (M ^<+> , 75), 529 (100), 332 (35). The emission spectrum is shown in FIG. 8, and the proton NMR spectrum is shown in FIG.

thpyIrsd. Chloride cross-linked dimer (thpyIrCl) ₂ (0.21 g, 0.19 mM) was treated in the same manner as (thpyIrCl) ₂ . Yield: 0.21 g, 84%. MS (EI): m / z (relative intensity) 647 (M ⁺ , 100), 513 (30), 486 (15), 434 (20), 324 (25). The emission spectrum is shown in FIG. 10, and the proton NMR spectrum is shown in FIG.

btIrsd. Chloride cross-linked dimer (btIrCl) ₂ (0.05 g, 0.039 mM) was treated in the same manner as (tpyIrCl) ₂ . Yield: 0.05 g, 86%. MS (EI): m / z (relative intensity) 747 (M ⁺ , 100), 613 (100), 476 (30), 374 (25), 286 (32). The emission spectrum is shown in FIG. 12, and the proton NMR spectrum is shown in FIG.

Ir (bq) ₂ (acac), BQIr. Chloride cross-linked dimer (Ir (bq) ₂ Cl) ₂ (0.091 g, 0.078 mM), acetylacetone (0.021 g), and sodium carbonate (0.083 g) were added in 10 ml of 2-ethoxyethanol. Mixed. The mixture until no dimer was detected by TLC, was refluxed in 10 h N _2. The reaction was then cooled and the yellow precipitate was filtered. The product was purified by flash chromatography using dichloromethane. Product: light yellow solid (91% yield). ¹ H NMR (360 MHz, acetone-d ₆ ), ppm: 8.93 (d, 2H), 8.47 (d, 2H), 7.78 (m, 4H), 7.25 (d, 2H), 7.15 (d, 2H), 6.87 (d, 2H), 6.21 (d, 2H), 5.70 (s, 1H), 1.63 (s, 6H). MS, e / z: 648 (M ^<+> , 80%), 549 (100%). The emission spectrum is shown in FIG. 14, and the proton NMR spectrum is shown in FIG.

Ir (bq) ₂ (Facac), BQIrFA. Chloride cross-linked dimer (Ir (bq) ₂ Cl) ₂ (0.091 g, 0.078 mM), hexafluoroacetylacetone (0.025 g), and sodium carbonate (0.083 g) were added to 10 ml of 2-ethoxyethanol. Mixed in. The mixture until no dimer was detected by TLC, was refluxed in 10 h N _2. The reaction was then cooled and the yellow precipitate was filtered. The product was purified by flash chromatography using dichloromethane. Product: yellow solid (69% yield). ¹ H NMR (360 MHz, acetone-d ₆ ), ppm: 8.99 (d, 2H), 8.55 (d, 2H), 7.86 (m, 4H), 7.30 (d, 2H), 7.14 (d, 2H), 6.97 (d, 2H), 6.13 (d, 2H), 5.75 (s, 1H). MS, e / z: 684 (M ^<+> , 59%), 549 (100%). The emission spectrum is shown in FIG.

Ir (thpy) ₂ (acac), THPIr. Chloride-bridged dimer (Ir (thpy) ₂ Cl) ₂ (0.082 g, 0.078 mM), acetylacetone (0.025 g), and sodium carbonate (0.083 g) were added in 10 ml of 2-ethoxyethanol. Mixed. The mixture until no dimer was detected by TLC, was refluxed in 10 h N _2. The reaction was then cooled and the yellow precipitate was filtered. The product was purified by flash chromatography using dichloromethane. Product: yellow-orange solid (80% yield). ¹ H NMR (360 MHz, acetone-d ₆ ), ppm: 8.34 (d, 2H), 7.79 (m, 2H), 7.58 (d, 2H), 7.21 (d, 2H), 7.15 (d, 2H), 6.07 (d, 2H), 5.28 (s, 1H), 1.70 (s, 6H). MS, e / z: 612 (M ^<+> , 89%), 513 (100%). The emission spectrum is shown in FIG. 17 (marked as “THr”) and the proton NMR spectrum is shown in FIG.

Ir (ppy) ₂ (acac), PPIr. Chloride cross-linked dimer (Ir (ppy) ₂ Cl) ₂ (0.080 g, 0.078 mM), acetylacetone (0.025 g), and sodium carbonate (0.083 g) were added in 10 ml of 2-ethoxyethanol. Mixed. The mixture until no dimer was detected by TLC, was refluxed in 10 h N _2. The reaction was then cooled and the yellow precipitate was filtered. The product was purified by flash chromatography using dichloromethane. Product: yellow solid (87% yield). ¹ H NMR (360 MHz, acetone-d ₆ ), ppm: 8.54 (d, 2H), 8.06 (d, 2H), 7.92 (m, 2H), 7.81 (d, 2H), 7.35 (d, 2H), 6.78 (m, 2H), 6.69 (m, 2H), 6.20 (d, 2H), 5.12 (s, 1H), 1.62 (s) , 6H). MS, e / z: 600 (M ^<+> , 75%), 501 (100%). The emission spectrum is shown in FIG. 19, and the proton NMR spectrum is shown in FIG.

Ir (bthpy) ₂ (acac), BTPIr. Chloride cross-linked dimer (Ir (bthpy) ₂ Cl) ₂ (0.103 g, 0.078 mM), acetylacetone (0.025 g), and sodium carbonate (0.083 g) were added in 10 ml of 2-ethoxyethanol. Mixed. The mixture until no dimer was detected by TLC, was refluxed in 10 h N _2. The reaction was then cooled and the yellow precipitate was filtered. The product was purified by flash chromatography using dichloromethane. Product: yellow solid (49% yield). MS, e / z: 712 (M ^<+> , 66%), 613 (100%). The emission spectrum is shown in FIG.

[Ir (ptpy) ₂ Cl] ₂ : IrCl ₂ .xH ₂ O (1.506 g, 5.030 mM) and 2- (p-tolyl) pyridine (3.509 g, 20.74 mM) in 2-ethoxyethanol (30 ml) ) Was refluxed for 25 hours. The yellow-green mixture was cooled to room temperature and 20 ml of 1.0 M HCl was added to precipitate the product. The mixture was filtered, washed with 100 ml of 1.0 M HCl, then with 50 ml of methanol and then dried. The product was obtained as a yellow powder (1.850 g, 65%).

[Ir (ppz) ₂ Cl] ₂ : IrCl ₂ .xH ₂ O (0.904 g, 3.027 mM) and 1-phenylpyrazole (1.725 g, 11.96 mM) were placed in 2-ethoxyethanol (30 ml). The solution was refluxed for 21 hours. The gray-green mixture was cooled to room temperature and 20 ml of 1.0 M HCl was added to precipitate the product. The mixture was filtered, washed with 100 ml of 1.0 M HCl, then with 50 ml of methanol and then dried. The product was obtained as a light gray powder (1.133g, 73%).

_{[Ir (C6) 2 Cl]} 2: IrCl 3 · xH 2 O (0.075g, 0.251mM) and coumarin C6 [3- (2-benzothiazolyl) -7- (diethyl) coumarin] [Aldrich (Aldrich)] A solution of (0.350 g, 1.00 mM) in 2-ethoxyethanol (15 ml) was refluxed for 22 hours. The dark red mixture was cooled to room temperature and 20 ml of 1.0 M HCl was added to precipitate the product. The mixture was filtered and washed with 100 ml of 1.0 M HCl, then with 50 ml of methanol. The product was dissolved in methanol and precipitated. The solid was filtered and washed with methanol until no green luminescence was observed in the filtrate. The product was obtained as an orange powder (0.0657 g, 28%).

Ir (ptpy) ₂ acac (tpyIr): [Ir (ptpy) ₂ Cl] ₂ (1.705 g, 1.511 mM), 2,4-pentanediol (3.013 g, 30.08 mM), and (1.802 g) , 17.04 mM) in 1,2-dichloroethane (60 ml) was refluxed for 40 hours. The yellow-green mixture was cooled to room temperature and the solvent was removed under reduced pressure. The product was taken up in 50 ml of CH ₂ Cl ₂ and filtered through celite. Removal of the solvent under reduced pressure gave the product as orange crystals (1.696 g, 89%). FIG. 22 shows the emission spectrum. The results of an X-ray diffraction study of the structure are shown in FIG. It was found that the nitrogen atom of the tpy (tolylpyridyl) group was in a trans form. From an X-ray study, the number of reflections was 4663 and the R factor was 5.4%.

_{Ir (C6) 2 acac (C6Ir} ): was added [Ir _(C6) 2 _{Cl] 2} of 2 drops of solution were placed in CDCl ₃ 2,4-pentanedione and an excess _Na 2 CO _3. The tube was heated at 50 ° C. for 48 hours, then filtered through a short celite plug in a Pasteur pipette. The solvent and excess 2,4-pentanedione were removed under reduced pressure to give the product as an orange solid. FIG. 24 shows light emission of C6, and FIG. 25 shows light emission of C6Ir.

Ir (ppz) ₂ picolinate (PZIrp): [Ir (ppz) ₂ Cl] ₂ (0.0545 g, 0.0530 mM), and picolinic acid (0.0525 g, 0.426 mM) in CH ₂ Cl ₂ (15 ml). Was refluxed for 16 hours. The light green mixture was cooled to room temperature and the solvent was removed under reduced pressure. The solid obtained was taken up in 10 ml of methanol and a light green solid precipitated out of solution. The supernatant was removed by decantation, the solid was dissolved in CH ₂ Cl _2, and filtered through a short plug of silica. Removal of the solvent under reduced pressure gave the product as light green crystals (0.0075 g, 12%). The emission is shown in FIG.

2- (1-Naphthyl) benzoxazole, (BZO-Naph). 11.06 g, 101 mM 2-aminophenol were mixed with 15.867 g, 92.2 mM 1-naphthoic acid in the presence of polyphosphoric acid. The mixture was heated and stirred at 240 ° C. for 8 hours under N ₂ . The mixture was cooled to 100 ° C. and water was added to it. The insoluble residue was collected by filtration, washed with water and reslurried then in excess of 10% Na ₂ CO _3. The alkaline slurry was filtered and the product was washed thoroughly with water and dried in vacuum. The product was purified by vacuum distillation. BP 140 ° C / 0.3mmHg. Yield 4.8 g (21%).

Tetrakis [2- (1-naphthyl) benzoxazole ^C 2, N] ^(μ- dichloro) _{diiridium, [(Ir 2 (BZO-} Naph) 4 Cl) 2]. Iridium trichloride hydrate (0.388 g) was combined with 2- (1-naphthyl) benzoxazole (1.2 g, 4.88 mM). The mixture was dissolved in 2-ethoxyethanol (30 ml) and then refluxed for 24 hours. The solution was cooled to room temperature and the resulting orange solid product was collected in a centrifuge tube. Four centrifugation / redispersion cycles were performed, washing the dimer with methanol followed by chloroform. Yield 0.66 g.

Bis [2- (1-naphthyl) benzoxazole] acetylacetonate, Ir (BZO-Naph) ₂ (acac), (BONIr). Chloride crosslinked dimer _{[Ir 2 (BZO-Naph)} 4 Cl] 2 (0.66g, 0.46mM), acetylacetone (0.185 g), and sodium carbonate (0.2 g), in dichloroethane 20ml Mixed. The mixture was refluxed for 60 h in _{N 2.} The reaction was then cooled and the orange / red precipitate was collected in a centrifuge tube. The product was washed with a water / methanol (1: 1) mixture, followed by four centrifugation / redispersion cycles, washing with methanol. An orange / red solid product was produced by sublimation. SP 250 ° ^{C./2×10 −5} Torr. Yield 0.57 g (80%). The emission spectrum is shown in FIG. 27, and the proton NMR spectrum is shown in FIG.

  Bis (2-phenylbenzothiazole) iridium acetylacetonate (BTIr): 2.1 mM 2-phenylbenzothiazoleiridium chloride dimer (2.7 g) was placed in 120 ml of 2-ethoxyethanol at room temperature. To the solution was added 9.8 mM (0.98 g, 1.0 ml) of 2,4-pentanedione. About 1 g of sodium carbonate was added and the mixture was heated to reflux in an oil bath for several hours under nitrogen. The reaction mixture was cooled to room temperature and the orange precipitate was removed by vacuum filtration. The filtrate was concentrated and methanol was added to further precipitate the product. Continuous filtration and precipitation gave a 75% yield. The emission spectrum is shown in FIG. 29, and the proton NMR spectrum is shown in FIG.

  Bis (2-phenylbenzoxazole) iridium acac (BOIr): A solution of 2.4 mM 2-phenylbenzoxazoleiridium chloride dimer (3.0 g) in a room temperature solution in 120 ml of 2-ethoxyethanol. , 9.8 mM (0.98 g, 1.0 ml) of 2,4-pentanedione was added. Approximately 1 g of sodium carbonate was added and the mixture was heated to reflux in an oil bath overnight (〜16 hours) under nitrogen. The reaction mixture was cooled to room temperature and the yellow precipitate was removed by vacuum filtration. The filtrate was concentrated and methanol was added to further precipitate the product. Continuous filtration and precipitation gave a 60% yield. The emission spectrum is shown in FIG. 31, and the proton NMR spectrum is shown in FIG.

  Bis (2-phenylbenzothiazole) iridium (8-hydroxyquinolate) (BTIrQ): 0.14 mM of 2-phenylbenzothiazoleiridium chloride dimer (0.19 g) was dissolved in 20 ml of 2-ethoxyethanol. To the room temperature solution, 4.7 mM (0.68 g) of 8-hydroxyquinoline was added. About 700 mg of sodium carbonate was added and the mixture was heated to reflux in an oil bath overnight (23 hours) under nitrogen. The reaction mixture was cooled to room temperature and the red precipitate was removed by vacuum filtration. The filtrate was concentrated and methanol was added to further precipitate the product. Continuous filtration and precipitation gave a 57% yield. The emission spectrum is shown in FIG. 33, and the proton NMR spectrum is shown in FIG.

  Bis (2-phenylbenzothiazole) iridium picolinate (BTIrP): 0.80 mM of 2-phenylbenzothiazoleiridium chloride dimer (1.0 g) was added to a solution at room temperature in 60 ml of dichloromethane. .14 mM (0.26 g) picolinic acid was added. The mixture was heated in an oil bath for 8.5 hours under nitrogen and brought to reflux. The reaction mixture was cooled to room temperature and the yellow precipitate was removed by vacuum filtration. The filtrate was concentrated and methanol was added to further precipitate the product. Continuous filtration and precipitation yielded about 900 mg of impure product. FIG. 35 shows the emission spectrum.

  Bis (2-phenylbenzoxazole) iridium picolinate (BOIrP): 0.14 mM of 2-phenylbenzoxazoleiridium chloride dimer (0.18 g) was added to a room temperature solution in 20 ml of dichloromethane at room temperature. 0.52 mM (0.064 g) picolinic acid was added. The mixture was heated in an oil bath overnight (17.5 hours) under nitrogen and refluxed. The reaction mixture was cooled to room temperature and the yellow precipitate was removed by vacuum filtration. The precipitate was dissolved in dichloromethane, transferred to a glass bottle, and the solvent was removed. FIG. 36 shows the emission spectrum.

  FIG. 37 shows comparative emission spectra of different L's in the btIr complex.

V. A. 2. c. Advantages Over Conventional Methods This synthesis has certain advantages over conventional methods. Compounds of formula PtL ₃ cannot be sublimed without decomposition. It is problematic to obtain a compound of formula IrL _3. Certain ligands react cleanly with Ir (acac) ₃ to give tris complexes, but more than half of the ligands we studied do not react cleanly in the following reactions: 3L + Ir (acac) ₃ → L _The yield of ₃ Ir + acacH, where L = 2-phenylpyridine, benzoquinoline, 2-thienylpyridine, is typically 30%.
A preferred route to the Ir complex can be by the chloride bridged dimer L ₂ M (μ-Cl) ₂ ML ₂ by the following reaction: 4 L + IrCl ₃ .nH ₂ O → L ₂ M (μ− Cl) ₂ ML ₂ + 4HCl
While less than 10% of the ligands we studied could not cleanly give Ir dimers in high yields, the ligands that work to be problematic due to the conversion of the dimers to the tris complex IrL ₃ are: There are only a few: L ₂ M (μ-Cl) ₂ ML ₂ + 2Ag ⁻ +2 L → L ₃ Ir + 2AgCl

We have found that a much more efficient method of producing phosphorescent complexes is to form phosphors using chloride bridged dimers. The dimer itself does not emit strong light, probably because it is strongly quenched by adjacent metal (eg, iridium) atoms. It has been found that chloride ligands can be replaced by chelating ligands to give stable octahedral metal complexes by the following chemical changes: L ₂ M (μ-Cl) ₂ ML ₂ + XH → L ₂ MX + HCl

  We have studied extensively the system for M = iridium. The obtained iridium complex emits strong light and has a life of 1 to 3 microseconds (μsec) in most cases. Such lifetimes indicate phosphorescence (see Charles Kittel, "Introduction to Solid State Physics"). The transition in these materials is metal ligand charge transfer (MLCT).

The detailed description below analyzes the emission spectra and lifetime data for a number of different complexes, all of which are L ₂ MX (M = Ir), where L is a cyclometallated (bidentate) configuration. And X is a bidentate ligand]. In most cases, the emission of these complexes is based on the MLCT transition between Ir and the L ligand, or on a mixture of that transition and the interligand transition. A special example is described below. According to theoretical and spectroscopic studies, the complex has an octahedral coordination around the metal (eg, in the case of the nitrogen heterocycle of the L ligand, there is a trans configuration in the Ir octahedron).

In particular, FIG. 1 gives the structure for L ₂ IrX in the case of L = 2-phenylpyridine, X = acac, picolinate (from picolinic acid), salicylanilide, or 8-hydroxyquinolinate.

V. A. 2. d. The slight changes in the synthetic pathway for producing the facial (facial) isomer to meridianal isomer L 2 _IrX, it is possible to form the meridianal isomers of formula L ₃ Ir. The previously disclosed L ₃ Ir complexes all have a facial configuration of chelating ligands. The formation and use of meridianal L ₃ Ir complexes as phosphors in an OLED are disclosed herein. Two structures are shown in FIG.

Facial L ₃ Ir isomers have been prepared by the reaction of L with Ir (acac) ₃ in refluxing glycerol, as described in Formula 1 (below). Preferred route to L ₃ Ir complexes are those according to formula 2 + 3 chloride crosslinked dimers by (below) _{[L 2 Ir (μ-Cl)} 2 IrL 2 ]. The product of Formula 3 is the same facial isomer as that formed from Ir (acac) ₃ . The advantage of the latter method of preparation, facial -L 3 _Ir yield is that even better. Good yields of the meridianal isomer are obtained if the third ligand is added to the dimer (without Ag +) in the presence of a base and acetylacetonate. Meridianal isomers do not convert to facial isomers by recrystallization, reflux in coordinating solvents, or sublimation. Two examples of these meridianal complexes, but mer-Irppy and mer-Irbq (Figure 3) is formed, it ligand which affords a stable facial _-L 3 Ir can be made meridianal form as well I believe.

(1) 3L + Ir (acac) ₃ → facial L ₃ Ir + acacH (where L = 2-phenylpyridine, benzoquinoline, 2-thienylpyridine) Typically, 30% yield.
(2) 4L + IrCl ₃ .nH ₂ O → L ₂ Ir (μ-Cl) ₂ IrL ₂ + 4HCl Typically yield greater than 90%. See attached spectrum for examples of L. All the ligands effective in (1) are sufficiently established.
_{(3) L 2 Ir (μ} -Cl) 2 IrL 2 + 2Ag ++ 2L → 2 facial _· L 3 Ir + 2AgCl typically 30% yield. Only (1) is sufficiently valid for the same ligand which is sufficiently effective.
(4) L ₂ Ir (μ-Cl) ₂ IrL ₂ + XH + Na ₂ CO ₃ + L → meridianal L ₃ Ir Typically yield greater than 80%. XH = acetylacetone.

Unexpectedly, the photophysical properties of the meridianal isomer are different from those of the facial form. This can be seen from the spectral details discussed below, which show a significant red shift and are broader in the meridianal isomer for their facial counterparts. The light-emitting line looks as if a red band was added to the characteristics of the facial L ₃ Ir. The structure of the meridianal isomer is similar to that of the L ₂ IrX complex, for example, with respect to the arrangement of the N atoms of the ligand around Ir. Especially when L = ppy ligand, the nitrogen of the L ligand is trans in both mer-Ir (ppy) ₃ and (ppy) ₂ Ir (acac). Furthermore one L ligand _mer-L 3 Ir complexes _has the same coordination as the X ligand of L 2 IrX complexes. To illustrate this point, the model of mer-Ir (ppy) ₃ is shown after (ppy) ₂ Ir (acac) in FIG. One of the ppy ligands of mer-Ir (ppy) ₃ coordinates at the Ir center in the same geometric state as the acac ligand of (ppy) ₂ Ir (acac).

The HOMO and LUMO energies of the L ₃ Ir molecule are clearly affected by the choice of isomer. These energies control the current-voltage characteristics and lifetime of OLEDs manufactured using these phosphors and are very important.

  The synthesis for the two isomers depicted in FIG. 3 is as follows.

[Synthesis of Meridianal Isomer]:
mer-Irbq: 91 mg (0.078 mM) of [Ir (bq) ₂ Cl] ₂ dimer, 35.8 mg (0.2 mM) of 7,8-benzoquinoline, 0.02 mg of acetylacetone (about 0.2 mM ), And 83 mg (0.78 mM) of sodium carbonate were boiled in 12 ml of 2-ethoxyethanol (as used) in an inert atmosphere for 14 hours. Upon cooling yellow-orange precipitate formed and was isolated by filtration and flash chromatography (silica _{gel, CH 2 Cl 2) (72} % yield). ¹ H NMR (360MHz, dichloromethane _{-d 2), ppm: 8.31 (} q, 1H), 8.18 (q, 1H), 8.12 (q, 1H), 8.03 (m, 2H), 7.82 (m, 3H), 7.59 (m, 2H), 7.47 (m, 2H), 7.40 (d, 1H), 7.17 (m, 9H), 6.81 (d , 1H), 6.57 (d, 1H). MS, e / z: 727 (100%, M ^<+> ). The NMR spectrum is shown in FIG.

mer-Ir (tpy) ₃ : IrCl ₃ .xH ₂ O (0.301 g, 1.01 mM), 2- (p-tolyl) pyridine (1.027 g, 6.069 mM), 2,4-pentanedione (0 .208g, 2.08mM), and _Na 2 _CO 3 _(0.350g, the solution was placed in a 3.30 mm) of 2-ethoxyethanol (30 ml), was refluxed for 65 hours. The yellow-green mixture was cooled to room temperature and 20 ml of 1.0 M HCl was added to precipitate the product. The mixture was filtered, washed with 100 ml of 1.0 M HCl, then with 50 ml of methanol, then dried, the solid was dissolved in CH ₂ Cl ₂ and filtered through a short plug of silica. did. The solvent was removed under reduced pressure to give the product as a yellow-orange powder (0.265 g, 38%).

V. A. 3. Possible host molecules The invention relates to the use of the above-mentioned dopants in a host phase. This host phase may consist of molecules having a carbazole moiety. Molecules falling within the scope of the present invention are included in the following:

  [Lines indicate possible substitution by alkyl or aryl groups at the available carbon atom (s) represented by the ring. ]

  Yet another preferred molecule having carbazole functionality is 4,4'-N, N'-dicarbazole-biphenyl (CBP), which has the formula:

V. B. 1. Utilization in Devices The device structures chosen for use are very similar to standard vacuum deposited ones. As an overview, a hole transport layer (HTL) is first deposited on an ITO (indium tin oxide) coated glass substrate. For devices that provide 12% quantum efficiency, the HTL consists of 30 nm (300 °) NPD. On the NPD, a thin film of an organic metal doped into a host matrix is deposited to form a light emitting layer. By way of example, the light-emitting layer was CBP containing 12% by weight of bis (2-phenylbenzothiazole) iridium acetylacetonate (referred to as BTIr), and the thickness of the layer was 30 nm (300 °). A blocking layer is deposited on the light emitting layer. The blocking layer consisted of bathocuproine (BCP) and had a thickness of 20 nm (200 °). An electron transport layer is deposited on the blocking layer. Electron-transporting layer consisted of Alq ₃ with a thickness of 20 nm. The device is completed by depositing a Mg-Ag electrode on the electron transport layer. It has a thickness of 100 nm. All depositions were performed at a vacuum less than 5 × 10 ⁻⁵ Torr. Devices were tested in air without packaging.

  When a voltage is applied between the cathode and the anode, holes are injected from the ITO into the NPD and transported by the NPD layer, while electrons are injected from MgAg into Alq and transported through Alq and BCP. Next, holes and electrons are injected into the EML, carrier recombination occurs in the CBP, an excited state is formed, energy transfer to the BTIr occurs, and finally the BTIr molecule is excited and radiatively decays.

As illustrated in FIG. 5, the quantum efficiency of this device is 12% at a current density of about 0.01 mA / cm ² .

Related terms are as follows: ITO is a transparent conductive phase of indium tin oxide that acts as an anode. ITO is a degenerate semiconductor formed by doping a broadband semiconductor. The carrier concentration of ITO is over 10 ¹⁹ / cm ³ . BCP is a layer that blocks excitons and transports electrons. Alq ₃ is an electron injection layer. Other hole transport layer materials may be used. For example, a TPD hole transport layer can be used.

  BCP serves as an electron transport layer and an exciton blocking layer, which layer has a thickness of about 10 nm (100 °). BCP is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (also called bathocuproine) and has the following formula:

Alq ₃ acting as an electron injection / electron transport layer has the following formula:

  Generally, doping is varied to achieve optimal doping.

V. B. 2. Incorporation of Fluorescent Ligands into Phosphorescent Complexes As noted above, fluorescent materials have certain advantages as emitters in devices. If the L ligand used to make the L ₂ MX (eg, M = Ir) complex has a high fluorescence quantum efficiency, efficient intersystem crossing in and out of the triplet state of the ligand is achieved. Therefore, strong spin-orbit coupling of Ir metal can be used. The concept is that Ir makes the L ligand an effective phosphorescent center. Using this method, any fluorescent dye can be used to make an effective phosphorescent molecule therefrom (ie, L fluoresces, but L ₂ MX (M = Ir) fluoresces). .

As an example, L ₂ IrX where L = coumarin and X = acac was produced. This is referred to as coumarin-6 (C6Ir). This complex gives intense orange emission, while coumarin itself emits green light. The spectra for both coumarin and C6Ir are given in the figure.

  Other fluorescent dyes would be expected to show similar spectral shifts. Since the number of fluorescent dyes developed for dye lasers and other applications is very large, this method is expected to result in a very wide range of phosphorescent materials.

In order to form a 5- or 6-membered metallocycle, a fluorescent dye having an appropriate functional group is required so that it can be metallated with a metal (for example, iridium). The L ligands we have studied to date all have sp ² hybridized orbital carbon and heterocyclic N atoms in the ligand, and thus can react with Ir to form a 5-membered ring.

V. B. 3. Potential degradation reactions, including carrier trap holes or electrons at the X or L ligand, may occur in the emissive layer. The resulting oxidation or reduction alters the phosphor and degrades performance.

  In order to obtain the maximum efficiency of a phosphor-doped OLED, it is important to control the holes or electrons that cause unwanted oxidation or reduction reactions. One way to do this is to trap carriers (holes or electrons) at the phosphorescent dopant. It is advantageous to trap carriers that are far from the atoms or ligands involved in the phosphorescence. Carriers thus trapped at a distance will readily recombine with intermolecularly opposite carriers or with carriers from neighboring molecules.

An example of a phosphor designed to trap holes is shown in FIG. The diarylamine group of the salicylanilide group is expected to have a HOMO level (based on electrochemical measurements) of 200-300 mV higher than that of the Ir complex, so that holes are trapped exclusively at the amine group. Become. Although the holes are easily trapped at the amine, the emission from this molecule will come from the MLCT and from the interligand transition from the Ir (phenylpyridine) system. Electrons trapped in this molecule are most likely to be in one of the pyridyl ligands. Intermolecular recombination will most likely result in exciton formation in the Ir (phenylpyridine) system. Since the trapping site is above the typical X ligand, which is not extensively involved in the luminescence process, the presence of the trapping site will not significantly affect the emission energy of the complex. Related molecules can be designed in which electron carriers are trapped far away from the L ₂ Ir system.

V. B. 4. As seen in the color adjustment IrL ₃ system, the emission color is strongly affected by the L ligand. This is consistent with luminescence including MLCT or interligand transitions. The emission spectra were very similar in all cases where we were able to produce both the Tris complex (ie, IrL ₃ ) and the L ₂ IrX complex. For example, Ir (ppy) ₃ and (ppy) ₂ Ir (acac) [acronym = PPIr] give an intense green emission with a λ _max of 510 nm. A similar trend is seen when comparing Ir (BQ) ₃ and Ir (thpy) ₃ with their L ₂ Ir (acac) derivatives, ie, in some cases the emission of light between the two complexes. There is no big gap.

However, in other cases, the choice of the X ligand affects both the energy and efficiency of the emission. The acac and salicylanilide L ₂ IrX complexes give very similar spectra. So far, the picolinic acid derivatives we have produced show a slight blue shift (15 nm) in their emission spectra for acac and salicylanilide complexes of the same ligand. This can be seen in the spectra of BTIr, BTIrsd, and BTIrpic. In all three of these complexes, we expect that the emission mainly comes from the MLCT and the reciprocal L transition, and that the picolinic acid ligand changes the energy of the metal orbitals, thereby affecting the MLCT band.

If an X ligand is used whose triplet level is lower in energy than the “L ₂ Ir” skeleton, emission from the X ligand can be observed. This is the case for the BTIrQ complex. In this complex, the emission intensity is very weak, centered at 650 nm. This is completely unexpected. This is because the emission of the system based on the BT ligand is all at approximately 550 nm. Light emission in this case is almost completely from Q-system transition. The fluorescence spectrum for heavy metal quinolates (eg, IrQ ₃ or PtQ ₂ ) is centered at 650 nm. The complex itself emits light with very low efficiency, <0.01. Both energy and efficiency of the L 2 _IRQ materials are consistent with emission based on the "X". If the emission from the X ligand or “IrX” system was efficient, this would have been a good red emitter. It is important to note that although all of the examples listed here are strong "L" emitters, this does not preclude good phosphors being formed from "X" based emissions. .

Poor selection of the X ligand can severely quench the emission from the L ₂ IrX complex. Both complexes hexafluoro -acac and diphenyl _-acac, when used as X ligands L 2 IrX complex, or give a very weak emission, or show no emission. It is not completely clear why these ligands quench emission so strongly, but one of these ligands attracts more electrons than acac and the other attracts more electrons. give. The spectrum of BQIrFA is shown in the figure. The emission spectrum of this complex is slightly shifted from BQIr, as expected from the much stronger electron withdrawing of the hexafluoroacac ligand. The emission intensity from BQIrFA is at least two orders of magnitude lower than BQIr. Due to this severe quench problem, complexes of these ligands were not studied.

V. C. Description of Other Molecules CBP was used in the device described here. The present invention is also effective with other hole transport molecules known to those skilled in the art to serve as the hole transport layer of the OLED.

  In particular, the invention is also effective with other molecules having a carbazole function or a similar arylamine function.

V. D. Use of the Device The OLEDs of the present invention can be used in virtually any type of device having an OLED, such as a large screen display, a vehicle, a computer, a television, a printer, a large area wall, a theater or a stadium. It can be used for OLEDs incorporated into screens, bulletin boards, or signs.

  The invention described herein may be used in conjunction with the following pending application: "High Reliability, High Efficiency, Integratable Organic Light Emitting Devices and Methods for Fabricating Same". and Methods of Producing Same), U.S. Patent Application Serial No. 08 / 774,119 (filed on December 23, 1996); "Movel Materials for Multicolor Light Emitting Devices", Serial No. 08 / 850,264 (filed on May 2, 1997); "Electron Transporting and Light Emitting Layers Based on Organic Free Raicals", Serial No. 08 / 774,120 (filed December 23, 1996) (published September 22, 1998 as US Pat. No. 5,811,833); "Multicolor Display Devices", Serial No. 08 / 772,333 (filed on December 23, 1996); "Red-Emitting Organic Light Emitting Devices (OLED's)", Serial No. 08 / 774,087 (filed December 23, 1996) (approved); "Driving Circuit For Stacked Organic Light Emitting Devices", Serial No. 08 / 792,050 (filed February 3, 1997) (published May 26, 1998 as U.S. Pat. No. 5,757,139); "High Efficiency Organic Light Emitting Device Structure" Light Emitting Device Structures), Serial No. 08 / 772,332 (filed December 23, 1996) (published November 10, 1998 as U.S. Pat. No. 5,834,893); "Vacuum deposited non-polymer flexible organic light emitting devices" (Vacuum Deposited, Non-Polymeric Flexible Organic Light Emitting Devices), Serial No. 08 / 789,319 (filed January 23, 1997) (published December 1, 1998 as U.S. Pat. No. 5,844,363); "Displays Having Mesa Pixel Structure" (Displays Having Mesa Pixel). Configuration), Serial No. 08 / 794,595 (filed on Feb. 3, 1997); "Stacked Organic Light Emitting Devices", Serial No. 08 / 792,046 (filed February 3, 1997) (published June 29, 1999 as U.S. Patent No. 5,917,280); "High Contrast Transparent Organic Light Emitting Device". Light Emitting Devices), Serial No. 08 / 792,046 (filed on Feb. 3, 1997); "High Contrast Transparent Organic Light Emitting Device Display", Serial No. 08 / 821,380 (filed on March 20, 1997); "Organic Light Emitting Devices Containing A Metal Complex of 5-Hydroxy-Quinoxaline as" A Host Material), Serial No. 08 / 838,099 (filed on April 15, 1997) (published Jan. 19, 1999 as U.S. Pat. No. 5,861,219); "Light Emitting Devices Having" High Brightness), Serial No. 08 / 844,353 (filed on April 18, 1997); "Organic Semiconductor Laser", Serial No. 08 / 859,468 (filed on May 19, 1997); "Saturated Full Color Stacked Organic Light Emitting Devices", Serial No. 08 / 858,994 (filed May 20, 1997) (published August 3, 1999 as U.S. Patent No. 5,932,895); "Plasma Treatment of Conductive". Layers), PCT / US97 / 10252 (filed on June 12, 1997); "Novel Materials for Multicolor Light Emitting Diodes", Serial No. 08 / 814,976 (filed on Mar. 11, 1997); "Novel Materials for Multicolor Light Emitting Diodes", Serial No. 08 / 771,815 (filed on December 23, 1996); "Patterning of Thin Films for the Fabrication of Organic Multi-color Displays", PCT / US97 / 10289 (filed June 12, 1997); and "Double Heterostructure Infrared and Vertical Cavity Surface Emitting Organic Lasers", filed May 8, 1998, PCT / US 98/09480; published March 23, 1998; U.S. Pat. No. 5,874,803; published January 13, 1998; U.S. Pat. No. 5,707,745; published December 30, 1997; U.S. Pat. , 703, 436; and published May 26, 1998, U.S. Patent No. 5,757,026. Each pending application is incorporated herein by reference in its entirety.

Claims (15)

Electron transport layer,
A hole transport layer, and a formula L ₂ MX, where L and X are different bidentate ligands, and L is a monoanionic bidentate coordinated to M by sp ² hybrid orbital carbon and nitrogen atoms. a ligand, M is seen containing a light-emitting layer containing molecules and host compounds of forming a is and octahedral complex is iridium), molecules of the formula L ₂ MX is phosphor, an organic electroluminescent luminescence device (however, the molecules of formula L ₂ MX is, excluding the organic electroluminescent device is a molecule selected from the group X in the formula consists of hexafluoroacetylacetonate and diphenyl acetylacetonate). An exciton blocking layer for retaining excitons substantially in the light emitting layer, wherein a band gap of the blocking layer is larger than an energy difference between a triplet and a ground state singlet of the host compound. 2. The organic electroluminescent device according to 1. L is 2- (1-naphthyl) benzoxazole, (2-phenylbenzoxazole), (2-phenylbenzothiazole), (2-phenylbenzothiazole), (7,8-benzoquinoline), coumarin, (thienyl) Pyridine), phenylpyridine, benzothienylpyridine, 3-methoxy-2-phenylpyridine, thienylpyridine, and tolylpyridine, wherein X is acetylacetonate (acac), salicylidene, picolinate, and 8 The device of claim 1, wherein the device is selected from the group consisting of: hydroxyquinolinate. 3. The device of claim 2, wherein the ionization potential of the exciton blocking layer is greater than the ionization potential of the host compound. M is iridium and L is 2- (1-naphthyl) benzoxazole, (2-phenylbenzoxazole), (2-phenylbenzothiazole), (2-phenylbenzothiazole), (7,8-benzoquinoline ), Coumarin, (thienylpyridine), phenylpyridine, benzothienylpyridine, 3-methoxy-2-phenylpyridine, thienylpyridine, and tolylpyridine, wherein X is acetylacetonate (acac), 2. The device of claim 1, wherein the device is selected from the group consisting of salicylidene, picolinate, and 8-hydroxyquinolinate. The device of claim 1, wherein L is a phosphor and L ₂ MX is a phosphor. The organic molecule of the host compound,
(Wherein the symbol of the line drawn through the aromatic ring means that any carbon in the ring may be optionally substituted by alkyl or aryl)
3. The device of claim 2, wherein the device is selected from the group consisting of: X has been selected such that there is at least a 15 nm difference in λ _max between L ₂ MX and L ₃ M , L ₃ M is a homoleptic iridium complex, and L is the L of said L ₂ MX. The device of claim 1 , wherein M is iridium . L ₂ MX _is made of _{L 2 M (μ-Cl)} 2 ML 2, device of claim 1. The device of claim 1, incorporated in a large display, a vehicle, a computer, a television, a printer, a large screen wall, a theater or stadium screen, a billboard, or a sign. Wherein L 2 _MX (wherein, L is monoanionic bidentate ligand coordinated to M by sp ² hybridized carbon and nitrogen atoms, M forms a is and octahedral complex is iridium) have a light emitting layer containing the molecules, the molecules of the formula L ₂ MX is phosphor, an organic light emitting device (however, the molecules of formula L ₂ MX is, X in the formula is hexafluoroacetylacetonate and diphenyl Excluding organic light-emitting devices that are molecules selected from the group consisting of acetylacetonates). A crosslinked dimer of formula _{L 2 M (μ-Cl)} 2 ML 2, wherein _L 2 MX (M were combined and Bronsted acid XH is a metal that forms octahedral complexes, L and X are mono- a step of forming an organic metal complex represented by an anionic bidentate ligand), preparation of the organometallic complex represented by the formula L ₂ MX for use in organic electronic devices, as defined according to claim 1 Method. The device of claim 1, wherein L is selected from the group consisting of:
2. The device of claim 1, wherein L is a substituted or unsubstituted phenylpyridine. Molecules of formula L ₂ MX has an emission lifetime of 1-3 microseconds, the device according to claim 1.